The formation and characterization of cyclodextrin functionalized polystyrene nanofibersproduced by electrospinning

Abstract

Polystyrene (PS) nanofibers containing the inclusion complex forming beta-cyclodextrin(β-CD) were successfully produced by electrospinning aimed at developingfunctional fibrous nanowebs. By optimization of the electrospinningparameters, which included varying the relative concentration of PS andβ-CD in the solutions, bead-free fibers were produced. Homogeneous solutions ofβ-CD and PS in dimethylformamide (DMF) were used with concentrationsof PS varying from 10% to 25% (w/v, with respect to DMF), andβ-CD concentrations of 1% to 50% (w/w, with respect to PS). The presence ofβ-CD facilitated the production of bead-free PS fibers even from lower polymerconcentrations as a result of the higher conductivity of the PS/CD solutions. Themorphology and the production of bead-free PS/CD fibers were highly dependent on theβ-CD contents. Transmission electron microscope (TEM) and atomicforce microscope (AFM) images showed that incorporation ofβ-CD yielded PS fibers with rougher surfaces. Thermogravimetric analysis (TGA) and directinsertion probe pyrolysis mass spectroscopy (DP-MS) results confirmed the presence ofβ-CD in the PS fibers. X-ray diffraction (XRD) spectra of the fibers indicated that theβ-CDmolecules are distributed within the PS matrix without any phase separated crystalline aggregates up to 40%(w/w) β-CDloading. Furthermore, chemical analyses by Fourier transform infrared (FTIR) spectroscopy studies confirmthat β-CD molecules are located within the PS fiber matrix. Finally, preliminaryinvestigations using x-ray photoelectron spectroscopy (XPS) and time-of-flight staticsecondary ion mass spectrometry (ToF-static-SIMS) show the presence of thecyclodextrin molecules in the outer molecular layers of the fiber surfaces. TheXPS and ToF-SIMS findings indicate that cyclodextrin functionalized PS webswould have the potential to be used as molecular filters and/or nanofilters forthe purposes of filtration/purification/separation owing to surface associatedβ-CD molecules which have inclusion complexation capability.